Directive antenna system



Jan. 11, 1949. c, WARREN Z,458,8$5

DIRECTIVE ANTENNA SYSTEM Filed Dec. 15, 1944 8 Sheets-Sheet 1 //v l/ENTOR C. A. WA RREN Jan. 11, 1949. c. A; WARREN DIRECTIVE ANTENNA SYSTEM 8SheetsSheet 2 Filed Dec. 15, 1944 Elks uWSi IN l/E N TOR y c.,4. WARREN0.3

A 7' TOR/V5 V Jan, 11, 1949. c. A. WARREN 2,453,385

/ DIRECTIVE ANTENNA SYSTEM Fi led Dec. 15, 1944' 8 Sheets-Sheet 5 FIELDSTRENGTH POWER GAP-AXIS THEORETICAL DIRECTIVE PATTERNS OFF AXISTHEORETICAL DIRECTIVE PA TTERNS wvavron CA. WARREN ATTORNEY C. A. WARRENDIRECTIVE ANTENNA SYSTEM Jan. 11, 1949.

Filed Dec.

8 Sheets-Sheet 4 asmom Him/381$ 073/1 lNl ENTOR By C A. WARREN Jan. 11,1949.

c. A. WAR REN DIRECTIVE ANTENNA SYSTEM Filed Dec. 15, 1944 8Sheets-Sheet 5 83 89 e um? 83 be? (Hanna 8) H19N381S 073/1 INVENTOR' CA.WARREN BY I 8 A TTORNE Y c. A. wAREN DIRECTIVE ANTENNA SYSTEM Jan. 11,1949.

8 Sheets-Sheet 6 1- Filed Dec. 15, 1944 asmoap mouse/1s 073/1 -4 m at INVENT'OR By CA. m4 RREN ATTORNEY C. A. WARREN DIRECTIVE ANTENNA SYSTEMJan. 11, 1949.

Filed Dec. 15, 1944- 8 Sheets-Sheet 7 /Nl/N7'OR 6 A. WARREN Q y.

A T TORNE Y Patented Jan. 11, 1949- DIRECTIVE ANTENNA SYSTEM Clifford A.Warren, Watchung, N. 1., assignor to Bell Telephone Laboratories,Incorporated, New York, N. Y., a corporation of New York ApplicationDecember 15, 1944, Serial No. 568,248 16 Claims. (Cl. 250-3335) Thisinvention relates to antenna systems and particularly to directiveantenna systems.

the amplitudes of the antenna currents, as disclosed in Patent2,419,205, granted on April 22, 1947, to C. B. H. Feldman. In the caseof a single parabolic reflector, the desired minor lobe reduction may besecured by tapering the energization or illumination of the reflector,as described in Patent 2,422,184, granted on June 1'7, 1947,

' antenna pattern, the single'primary lobe of the to C. C. Cutler. Whilethese prior art methods have been successfully employed, they are notentirely suitable for reducing the minor lobes obtained in the doubleantenna or dual refiector system disclosed in the copending jointapplication of W. H. C. Higgins and applicant, Serial No. 453,390, filedon August 3, 1942, now Patent No. 2,424,982, dated August 5, 1947. Thedual reflector system comprises two parallel horizontal arrays ofcolinear dipoles and a separate large cylindrical parabolic reflectorassociated with each array, and it is especially suitable for use in adual plane lobe switching radar antenna system. Accordingly, it appearsdesirable to reduce the minor lobes, in the directive pattern of a dualreflector system, in a more satisfactory manner than heretoforeeffected.

It is one object of this invention to secure, in an antenna system, ahighlysatisfactory directive characteristic.

It is another object of this invention to reduce, in a directive antennasystem, the minor lobes of the directive characteristic of the antenna.

It is another object of this invention to reduce, in a dual plane lobeswitching antenna system, the first minor lobes of the directivepatterns taken in the two perpendicularly related switching planes,without materially increasing the half power widths of the major lobesin said patterns.

It is a further object of this invention to eliminate, in a dual planelobe switching antenna system, false cross-overs ,in each switchingplane.

In accordance with one embodiment of the invention, an auxiliary antennasystem is positioned adjacent to the dual reflector or main antennasystem disclosed in the eopending Higgins-Warren application and isutilized for securing the desired minor lobe reduction. For convenience,the single primary lobe of the main .minor lobes.

have opposite phases.

auxiliary antenna pattern and the single primary lobe of the resultantor combined pattern are termed herein the major" lobe, the maximum" lobeand the principal lobe, respectively; and the secondary lobes of themain, auxiliary and resultant patterns are termed herein the "minor,"the minimum" and the "subsidiary" lobes, respectively.

The auxiliary antenna system comprises a single cylindrical parabolicreflector and a: pair of colinear dipoles aligned with the horizontalfocal line of the small reflector. The auxiliary antenna system and themain antenna system are connected to the same radar transceiver. Thevertical aperture dimension of the auxiliary reflector and thehorizontal dimension of the auxiliary antenna system are relativelysmall compared to the corresponding dimensions of the main antennasystem and are such that, in each switching plane, the width of themaximum lobe pattern of the auxiliary antenna system is at least asgreat as the total width of the major lobe, the nulls adjacent theretoand the first Amplitude control means are provided for regulating thecurrents supplied to or received from the two antenna systems, wherebythe intensities of the maximum lobe of the auxiliary antenna and theaforementioned minor lobes may be equalized substantially. In each planethe two first minor lobes of the main antenna system are cophasal, andthe major and first minor lobes of the main antenna system During thedual plane lobe switching operation, the phase of the major lobe remainsconstant. A phasecontrol means is inserted in the line to the auxiliaryantenna system for securing an auxiliary antenna maximum lobe having aphase similar to that of the major lobe and opposite that of the firstminor lobes.

The invention will be more fully understood from a perusal of thefollowing specification taken in conjunction with the drawing on whichlike reference characters denote elements of similar function and onwhich:

Fig. 1 is a perspective front view of one embodiment of the invention;

Figs. 2and 3 are, respectively, a front diagrammatic view and a sidediagrammatic view of the embodimentof Fig. 1;

Figs. 4 and 5 are theoretical one-way directive patterns used forexplaining the invention;

Figs. 6, '7, 8 and 9 are measured one-way dior secondary antenna member2 and a lower cylindrical parabolic reflector or secondary antennamember 3, each having a horizontal axis 4. a horizontal focal line I, acommon vertical latus rectum 6, an opening or aperture 1, and a focaldistance d of a quarter wavelength. The apertures are relatively largeand of equal size and, in the case of each reflector, the longitudinaldimension m is approximately equal to twice the transverse dimension n,so that the entire aperture of the main antenna comprising the tworeflectors 2, 3 is substantially square. The axes 4, Fig. 3, areparallel to the on-axis or zero degree transceiving direction 8 whichcoincides with the equi-intensity direction for the dual plane lobeswitching system or, stated differently, coincides with the axis of thescanning cone.

Reference numeral 8 denotes an auxiliary antenna system comprising acylindrical reflector l cally related to the dimensions of reflectors 2and 3. As explained below, in one embodiment having a design or meanoperating wavelength of about 30.5 centimeters the side dimension a ofthe square opening i3 is two wavelengths and the side dimension m, or2n, of the square opening for the two reflectors 2 and 3' is about sixwavelengths. In other words, the dimension a is in the. order ofone-third of dimension 111..

As shown in Fig. l, the main antenna system I and the auxiliary antennasystem 9 are supported by a yoke assembly comprising a rotatablevertical shaft and bearing l4, a horizontal turntable member i6 attachedto shaft I4 and a pair of uprights or vertical arms IS. The tworeflectors 2, 3 are secured to a framework comprising two side membersl1 (only one shown in Fig. 1) which are mounted on a rotatablehorizontal shaft l8. Shaft I8 is supported on bearings IS in arms I6. Asindicated by arrows -20, means (not shown) are provided for rotating theentire antenna system' in the horizontal or azimuthal plane and fortilting it in the vertical or elevational plane. The auxiliary antennasystem is supported by struts 2| extending through reflectors 2 and 3and attached to the framework mentioned above.

Referring to Fig. 2, reference numerals 22 and 23 denote the primaryantennas associated with the upper and lower reflectors 2, 3,respectively,

' of the main antenna system. Each primary antenna comprises eightdipoles 24 arranged in a linear array and aligned with the reflectorfocal line and each array 22, 23 comprises two subarrays of fourcolinear dipoles. For convenience, the left upper, right upper, leftlower and right 23, denotes a translation device, such as a radartransceiver, which is connected by the coaxial principal line 24 and thecoaxial main line to the junction 3| of two coaxial array lines 32, oneof which is connected to the junction 33 of the two subarray lines 21associated with subarrays LU and EU and the other of which is connectedto the junction 34 of the two subarray lines 21 associated withsubarrays LD and RD. Each of the above-mentioned coaxial lines comprisesan inner conductor 33 and an outer conductor 38.

As is apparent from the drawing, the sixteen dipole lines 23 have equallengths, the eight branch lines "have equal lengths. the four subarraylines 21 have equal lengths and the two array lines 32 have equallengths, so that the paths connecting device 28 to the. sixteen dipoleshave equal electrical lengths. Numeral 3'! denotes an adjustableamplitude control means, such as an adjustable attenuator, included inthe main line 30.

Reference numerals 33 denote four short-circuited quarter-wave coaxiallines each of which is bridged across a different subarray line 21 at apoint a short distance from the junction 33 or 34, as explained inthecopending Higgins-Warren application. Numeral 33 denotes a lobe switcherhaving a base member 40, four stator plates 4| lower subarrays aredenoted LU, RU, LD and RD,

respectively. The four dipoles 24 in each of the four subarrays areconnected by four individual coaxial dipole lines 25 and two coaxial.branch lines 28 to a coaxial subarray line 21. Numeral and a rotor 42designed for capacitive association with two stator plates. Each statorplate 4| is connected to the inner conductor 33 of a coaxial phasingline 43 through a different switch 44, and the outer conductors 38 ofphasing lines 43 are connected to base member 40. The other ends of thefour phasing lines 43 are each connected to the approximate midpoint ofa different quarter-wave coaxial line 38 so that, as explained below, inthe case of each of lines 38, the rotor 42 applies the correct capacityto the midpoint of the line. Preferably, the phasing lines 43 havenegligible lengths, or lengths each equal to an odd multiple of a halfwavelength. In one actual embodiment the phasing lines 43 are omittedand the capacity is successively applied directly by the rotor 42 to themidpoints of the four quarterwave lines 38 which project into the lobeswitcher 39. Numerals 45 and 46 denote a motor and shaft for driving therotor 42. The main antenna system just described is basically the sameas that disclosed in the Higgins-Warren application, the primarydifference between the two systems being that the phasing lines 43 inthe system of the aforementioned application are each connected to thesubarray line v2'I through a halfwave line instead of a portion of ashort-circuited quarter-wave line 38.

Reference numeral 4! denotes the primary antenna associated with thereflector ill of the auxiliary antenna systemv 3. The primary antenna 41comprises two spaced dipoles 24 alignedwith the focal line H of theauxiliary reflector Ill. The two dipoles 24 are connected by the dipolelines 23, the coaxial auxiliary line 48 and the principal line 29 to thetranslation device 28. The auxiliary line 48 includes an adjustableattenuator 31 and an adjustable phase shifter 48.

In accordance with conventional practice, adiustable impedancetransformers (not shown) are inserted at the line junctions'and at thedipole junctions, for the purpose of matching the impedances throughoutthe system. A conventional short-clrcuited quarter-wave stub (not shown)is provided at the center of each dipole for rigidly connecting theinner coaxial line conductor 35 to the outer coaxial line conductor 38through a auaaea' high impedance. If desired, instead of employing thetwo special attenuators '31, the amplitude of the current delivered tothemain antenna I may be controlled by the impedance transformer atthejunction 66 of the principal line 26 and the main line 36, and theamplitude of the current supplied to the auxiliary antenna 8 maybecontrolled by the impedance transformer at the junction 60 of theprincipal line 26 and the auxiliary line 48.

In operation, assuming device 28 is aradar transceiver, pulsed energy isconveyed through the adjustable attenuator 81, and over lines 29, 36,82, 21, 26 and 26, between the device 26 and the sixteen dipoles 26 ofthe main antenna system i. At the same time, pulses are conveyed throughthe adjustable attenuator 31 and adjustable phase shifter 69, and overlines 26, 68 and 26, between device 28 and the two dipoles 24 of theauxiliary antenna system 9. As is now well understood,

the high frequency pulses emitted by the combined antenna system i, 6are, after reflection at a target, returned thereto as echo pulses.Since only the transmitting operation of the antenna systems i, 9 isdescribed in detail herein, it should be pointed out here that thetransmitting and receiving directive patterns are, by virtue of thereciprocity theorem, substantially the same.

Considering in detail the operation of the main antenna system i takenalone, with the four switch members M open, and motor 65 inactive, thelobe switcher 39 is disconnected from the four quarter-wave lines 38 andthe energies delivered to the sixteen dipoles 24 are cophasal. Thequarter-wave linestfi remain bridged across lines 21 but they do notaffect the phases of the currents in the subarray lines 21, since theyhave a high impedance. With the switches 66 closed, and with motor t6driving the rotor 62 clockwise, the rotor becomes capacitivelyassociated with the upper pair, right pair, lower pair, and left pair ofstator plates in succession, whereby two separate capacitive impedances,each comprising the rotor 62 and one of the stator plates ll, aresimultaneously connected through two phasing lines 63 and associatedquarter-wave lines 36 across two of the subarray lines 21, a capacitiveimpedance being connected successively across the four subarray lines21. a capacitive impedance is bridged across any of the fourquarter-wave lines 66, the electrical length, and impedance, of thequarter-wave line is changed to a value which affects the phase of thecurrent in the associated subarray line 21. Each capacitive impedanceretards the phase of the current, say about sixty degrees, in thesubarray line 27 to which it is momentarily connected. Hence, the lobeswitcher functions to change the phase of one-half of the sixteendipoles relative to the other half, the phases of the upper half, righthalf, lower half and lefthalf being changed in succession. With the lobeswitcher operating, the beam or direction of maximum action for theantenna system i is positioned off-axis, that is, at an angle to theon-axis direction 8, and as rotor 62 rotates, lobe switching between theup" and down beam positions and between the "left? and "right" beampositions is obtained, as explained in the Higgins-Warren application.The cone angle is dependent upon the value of the capacitive impedancementioned above and in one system is about three degrees. The directionof maximum action for the system may be aligned with the on-axisdirection 8 by opening the four switches 44.

In other words, when Ecplanatorv directive patterns Referring to Fig. 4and assuming switches 44 are open, curve 6! illustrates a theoreticalon-axis directive pattern for the main antenna system i taken alone. Theon-axis pattern 8| includes a major lobe 62, first nulls 66, first minorlobes 54, second nulls 66, second minor lobes 66, third minor lobes 51and fourth minor lobes 66. In Fig. 5 curve 58 illustrates a theoreticaloil-axis directive pattern for the main antenna system I taken alonewhen the switches 44 are closed. The off-axis pattern 58 includes amajor lobe 66, first nulls 6i, first minor lobes 82, second nulls 63,second minor lobes 64, third minor lobes 66 and fourth minor lobes 66.Each of curves 6i and 68 represents either the electric or magneticplane pattern, the electric or E-plane being horizontal and the magneticor H-plane being vertical inasmuch as the dipoles 26 are horizontal.

In each of patterns 8! and 59, the first minor lobes are cophasal andhave a phase opposite to that of the major lobe, as shown on thedrawings by the plus and minus signs. Assuming the phase of the majorlobe 62 of the on-axis pattern Si is zero, the phase of the major lobe66 of the oilaxis pattern 69 is not zero but is --30 degrees, inasmuchas the lobe switcher introduces a lag of 60 degrees in one half thedipoles and does not affect the phase in the other half of the dipoles.It may be pointed out that if a lobeswitcher were employed whichintroduces a phase change of +30 degrees in one half of the dipoles anda phase change of 30 degrees in the other half of the dipoles, the majorlobes 62 and 66 of patterns iii and 69 would have the same phase. Thelobing or beam direction would be the same in both cases since, in sofar as directivity is concerned, it is immaterial whether the 60 degreeout-of-phase relation is secured by retarding the phase of onehalf thesystem and leaving the phase of the other half the same, or by retardingthe phase of onehalf the system 30 degrees and advancing the phase ofthe other half of the system 30 degrees.- In practice, it is morepractical to use a simple lobe switcher, such as the switcher 39 which,as already stated, changes the phase of only onehalf the dipoles.

It will be observed that the first minor lobes 66, Fig. 4. aresymmetrical on each side of the major lobe 62 and that these minor lobesare of substantially the same amplitude. As shown in Fig. 5, when themajor lobe B0 is shifted to one side of the on-axis direction 8 theintensity of the first minor lobe 62 on the opposite side of the on-axisdirection 6 is increased considerably,

and this first minor lobe 62 assumes a position closer to the .on-axisdirection 6. On the other hand, the intensity of the first minor lobe 62on the same side of axis 8 as the shifted major lobe is decreased, andthis first minor lobe assumes a position farther away from axis 8. Thefirst minor lobes 56 and 62 of patterns 6i and 59 for the main antennasystem I, that is, for a prior art system such as that disclosed in theHiggins- Warren application, are highly detrimental and may, in radaroperation, cause false crossovers and ambiguous indications. As will nowbe explained in connection with Figs. 4 and 5, the

auxiliary antenna system 9 utilized in accordance with the invention,functions to eliminate or at least reduce substantially the first minorlobes 56 and 62 which are otherwise present when switches 44 are eitheropen or closed.

Referring first to theon-axis explanatory directive patterns, Fig. 4,reference numeral 61 decases notes ideal or theoretical maximum lobepattern, talien in either the E-plane or the H-plane, of the auxiliaryantenna system 8. The maximum lobe has an angular width, taken at the 50per cent or half-power point. which is primarily a function of the sizeof the auxiliary refiector opening it, and an amplitude or heightdependent upon the adjustment of the attenuator 48. By selecting anopening l8, Fig.- 3, of proper size, asby adjusting the opening in acutand-try manner and by properly adjusting the attenuator 48, a maximumlobe may be obtained having a width and a height, that is, a shape, suchas shown in Fig. 4. The maximum lobe 61, it will be observed, overlapsthe major lobe 82 and the first minor lobes 84 and has. at its base, anangular width greater than. that portion of the main antenna pattern 8|which includes the two first minor lobes 84. the first nulls 88 and themajor lobe 52. The phase of the maximum lobe 81 is adjusted, by means01' phase shifter 48, so that the major lobe 52 and the maximum lobe 61are cophasal, and the cophasal first minor lobes 84 and the maximum lobe81 are opposite in phase or antiphasal. Since the major lobe 52 has aconstant zero phase when in the onaxis position shown in Fig. 4, thephase of the maximum lobe 81 for this condition is also zero.

The two fields from themain system I and the auxiliary system 8 addtogether in space to produce the resultant or combined pattern 88havin'g'a principal lobe 88, first nulls 10, first subsidiary lobes 1!,second subsidiary lobes 12, and third subsidiary lobes 18. Morespecifically,

' for the on-axis direction 8, the amplitude or field intensity Em ofthe major lobe 52 and the amplitude Ea of the maximum lobe 61 combine toproduce a maximum resultant intensity Em+Ee, since in direction 8 thetwo lobes 52, 81 are cophasal'. On the drawing, however, the unequalmaximum amplitudes of the major lobe 82 and principal lobe 68 are, forthe sake of simplicity, shown equal.

Considering, for purpose of explanation, onehalf of the two patterns,for example, the pattern portions included in the angular sector at theleft of axis 8, as the direction orangle increases from zero theamplitude of the major lobe 52 decreases, in accordance with the slopeor shape of the lobe, to zero at the first null 53.

In the angular sector or angle included between the on-axis direction 8and the first null 88, the amplitude of the maximum lobe 81 is fairlyconstant and, since lobes 52 and 61 are cophasal, the portions of lobes52 and 61 included in this small sector add to form one-half of thecentral portion of the principal lobe 89 of the resultant pattern 88.Considering the angular direction coincident with the the null direction53, the intensity of the principal lobe 88 is equal to the intensity ofmaximum lobe 61. In the angular sector included between the null 88 andthe axis 14, that is, the direction of maximum action, of the firstminor lobe 54, the amplitude of the main antenna pattern i increases, inaccordance with the shape of this minor lobe. Since the first minor lobe54 and the maximum lobe 81 are antiphasal, as previously explained, theamplitude of the resultant pattern 88 in this angular section will beequal to the diflerence between the amplitudes of the maximum lobe 81and the first minor lobe 54. At the oil-axis direction at which the twoamplitudes are equal, that is, at the point 15, at which the lobes orcurves I4 and 61 intersect, the amplitude of the resultant pattern 88iszero and the first null 18 of the reand null II, the maximum lobe 81and the first minor lobe 84 oppose each other and the small diil'erencebetween their intensities forms a portion of the first subsidiary lobe1i of the resultant pattern 88. It will be noted that the maximum lobe81 slightly'overlaps the second minor lobe I8. Preferably, theoverlapping should be kept to a minimum, by proper adjustment of theshape of the maximum lobe 81, inasmuch as the maximum lobe 81 and thesecond minor lobes' B8 are cophasal. Since both halves of pattern 8! andboth halves of maximum lobe 81 are symmetrical about, axis 8, thepattern portions at the right of axis 8 combine to produce the righthalf portion of pattern 88, in the manner explained above.

Referring now to the oil-axis explanatory directive patterns, Fig. 5,reference numeral 18 designates the maximum lobe, taken ineither theE-plane or the H-plane, of auxiliary antenna pattern. The lobe 16 is thesame, except as to phase, as the'lobe 81, Fig. 4. In this discussion itis assumed that the main antenna is lobe than that portion of the mainantenna pattern 69, which includes the two first minor lobes 62, thefirst nulls 8i and the major lobe 80. As previouslyexplained, the phaseof the major lobe is 30 degrees and phase shifter 49, Fig. 2, isadjusted so'that the maximum lobe 18 has a -30 degree phase, wherebythemajor lobe 60 and the maximum lobe 18 are cophasal, and the maximumlobe 18 and the cophasal first minor lobes 82 are anti-phasal. Inpractice, if desired, after final adjustment of the phase shifter 49,the shifter may be replaced by a section of coaxial line having theproper length to effect the desired phase shift, that is, to securecophasal maximum and major lobes. While the length of the coaxial linepath connecting junction to any main antenna dipole and the length ofthe coaxial line path connecting junction '58 to any auxiliary antennadipole differ by an amount necessary to secure cophasal maximum andmajor lobes, these lengths should nevertheless be comparable in orderthat the cophasal relation of the maximum and major lobes may bemaintained, substantially over the frequency range of the system.

The two fields from the main system I and the auxiliary system 9 addtogether in space to produce the resultant pattern 11 having a principallobe 18, a broad or flat null 18 on the left or shift" side of axis 8, asharp null 88 and a first subsidiary lobe or pip 8| on the right sidecorresponding in position to the fiat null 18, the second subsidiarylobes 82, third subsidiary lobes 83 and fourth subsidiary lobes 84. More.particularly, the amplitude of the maximum lobe 18, when adjusted foroptimum interaction with the pattern It. .Fig. 4, for the on-axiscondition or position of the major lobe of system I, as explained above,

is also optimum for the cut-oi! axis condition resultant principal lobe18 having an amplitude Em+Ea. As shown in Fig. 6, the particular first iminor lobe 62 the amplitude oi which is increased upon shift of majorlobe 60, namely, the righthand first minor lobe 62, assumes a positioncloser g to the axis 8 of the maximum lobe i6 and therefore interacts,as is desired, with a portion of the maximum lobe 16 having a highamplitude. .On the other hand, the left-hand minor lobe 62 having adecreased amplitude assumes a position far- 16 ther away from axis .9and therefore interacts, as is desired, with a portion of maximum lobe76 having a low amplitude. Inother words, when the beam is shifted, oneof first minor lobes ,62 increases in intensity and climbs cellationoccurs and the firstuninor lobes 62 are eliminated or at leastmaterially reduced. The right or high first minor lobe 62 extends above,and the left or low' first minor lobe 62 Just reaches, the maximum lobe16. ,-In practice, the attenuator 69 is adjusted to a value at whichboth first minor lobes 92 are reduced to a compromise value. As shown inFig. 5 the left or low minor lobe 92, and the maximum lobe I6 inantiphase therewith, combine to produce the fiat null 19 ofthe resultantpattern 17. The right or high first 3o minor lobe 62, and the maximumlobe 16 in antiphase therewith, combine to produce the sharp null 90 andthe pip or first subsidiary lobe 6! of the resultant pattern Ti.

For both the on-axiscondition, Fig; 4, and the oil-axis condition, Fig.5, it will be observed that the second, third and fourth minor lobes ofthe main antenna pattern are considerably lower in intensity than thefirst minor lobe. In Fig.4, the

second, third and fourth minor lobes 56, 51 and 56' 4o correspondrespectively, to the first, second and third subsidiary lobes II, 12 and19 of the resultant pattern 69. Now, as stated before, the maximumamplitude of the major lobe 52 is Em whereas the maximum amplitude ofthe principal 4 4 tem, as obtained with the auxiliary antenna syslobe 69is Em-l-Ea so that, although minor lobes 56, 57 and 58 do not interactwith the maximum lobe 67, the maximum amplitudes ofthe subsidiary lobesll, 12 and 19 are each only a small percentage of the resultantprincipal lobe 69, whereas the maximum amplitude of the correspondingminor lobe is a somewhat larger percentage of the major lobe 52.Similarlyxin Fig. 5, the maximum amplitudes of the subsidiary lobes 8i,82,

83 and 84 are each a relativel small percentage of principal lobe 18,whereas the maximumamplitudes of minor lobes 64, 65 and 66. are each asomewhat larger percentage of the major lobe 6D. In short, as shownabove, for both the on-axis condition, Fig. 4, and the off-axiscondition, Fig. 60

5, the auxiliary antenna functions to reduce materially or obliteratethe first minor lobes of the main antenna pattern or, in other words, toproduce in cooperation with the main antenna system a resultant patternhaving atthe positions of the first minor lobes very insignificantsubsidiary lobes, the maximum amplitudes of which are determinedprimarily by the ratio of the amplitudes of the higher order minor lobesand the maximum amplitude, not of the major lobe, but

of the principal lobe. Also the auxiliary antenna produces a resultantprincipal lobe having a high ain, as measured along. the axisof theprincipallobe.

For purpose of explanation, it has been assumed 7.5

up to a high 5 system I 16 i that the main antenna patterns for theE-plane and the H-planeare the same and accordingly that the idealauxiliary patterns are the same for that when the maximum lobe patternis cophasal with the major lobe pattern in one plane, say the E-plane,it is also cophasal in the other plane, that is, the H-plane;

Measured oneeway directive patterns tion to that illustrated by Figs. 1,2 and 3. More particularly, Fig. 6 illustrates the E-plane resultantpattern when the beam is" switched up (or down) or, stated difierently,when the resultant principal lobe is on-axis in the E-plane and oilaxisinthe H-plane. Fig. 7 illustrates the E-plane resultant pattern when thebeam is switched left (or right) or, stated differently, when theprincipal lobe is off-axis in the E-plane and on-axis in the H-plane.Fig. 8 illustrates ,the H-plane resultant Dattem when thebeam is lobedleft (or right), that is, when the principal lobe is on-axis in theH-plane and oiT-axisin the E- plane. Fig. 9 illustrates the H-planeresultant pattern when the beam is lobed up (or down) that is, when theprincipal lobe is off-axis in the Roughly,

represent the patterns for the main antenna system 9 completely removedfrom the structure. Hence, these curves illustrate the patterns obtainedwith a prior art systemsuch as that disclosed in Higgins-Warrenapplication. The dashdot E-plane curves 69, Figs. 6 and 7, are identicaland the. dash-dot'H-plane curves-90, Figs. 8 and 9, are identical; andthese four-curves illustrate the directive patterns for the auxiliaryantenna system taken apart from the main antenna The full line curvesSi. 92. 9.3 and 94 in Figs. 6, 7, 8 and 9 respectively, illustrate theresultant patterns obtained for the combined system comprising the mainand auxiliary antennas l, 9. Generally speaking, the main antennapatterns 85, 86, 81 and 89 each include a major lobe v Considering theE-plane patterns and,

Figs. 6 and 7, for'the main antenna system I,

taken alone, it will be noted that for the on-axis condition in theE-plane, Fig. 6, the maximum amplitudes of the first minor lobes 91 areabout 23 per cent-of the maximum amplitude of the 11 major lobe 88. Forthe off-axis condition in the l-plane. Fig. 'I, the left first minorlobe 81 which on the oppositeside of axis 8'from the beam hift, has amaximum amplitude of about 43.5 ner cent and is closer to axis 8 thanthe.left or :orresponding first minor lobe of Fig. 6. On the and 88,Figs."8 -and 9, for the main antenna sysforethe tern, taken alone,it-will be observed that on-axis position in the H-plane, Fig. 8, themaximum amplitudes of the first minor lobes 81 are about 28 per cent ofthe maximum amplitude of r the major lobe 88 and therefore slightlygreater than the maximum amplitudes of the first minor lobes 81 in theE-plane pattern 88, Fig. 6. for the on-axis condition in the E-plane.For the off-' axis condition in the H-plane,'Fig. 9, the left firstmindrlobe 81, which is on the side of axis 8 opposite from, the beamshift, has a maximum amplitude of 45.7 per cent and is slightly closerto the axis 8 than the left first minor lobe 81 of Fig. 8. On thecontrary, 81, Fig. 9, which is on the same side of axis 8 as the beamshift, has a maximum amplitude of about 23.7 per cent and is fartherfrom axis 8 than the right first minor lobe 81 of Fig. 8. Note that inthe E-plane and H-plane the two minor lobes 81 which increase inamplitude increase about the same amount, that is, 48.5 and 45.7 percent;

, Considering the auxiliary antenna patterns 88 and 88, Figs. 6, 7, 8and 9, the minimum lobes I88 have, generally speaking, a maximumamplitude of about21 per cent of the maximum amplitude of the maximumlobe 88 and about 6 per cent of the principal lobe I8I of the resultantpattern 8I. Hence; as is desired, these minimum lobes I88 are almostnegligible. If desired, the minimum lobes I88 may be further reduced byusing more than two, for example four, properly spaced dipoles in theprimary antenna 41 of the auxiliary antenna system 8 and by tapering theintensities of the dipole currents.

The mere presence of the auxiliary. antenna system, particularly theauxiliary reflector I8, when disconnected from the translation device28, causes a slight decrease in the width of the 1 main antenna majorlobe 85 and a slight increase in the intensities of the two first minorlobes 81. Accordingly, in practice, the amplitude control means 48,'Fig.2, associated with the auxiliary antenna system, is adjusted so that themaximum lobe and the enlarged first minor lobes mutually cancel. In thecase of transmitting, in order to compensate for the change produced inthe main antenna patterns 85, 88, 81 and 88, by the blocking effect ofthe auxiliary reflector, a

slight increase in the power or energy supplied to the auxiliary'antennasystem is required. This increase in power willnot increase the width ofthe resultant principal lobe -.I8J, since the tendency of this lobe toincrease is compensated by the decrease in width of the major lobe 85produced by the passive action of the auxiliary reflector I8. In onetested embodiment, it was found that the desired minor lobe suppressionwas achieved when energies of equal intensities assumes the right firstminor lobe "i2. were supplied to, or received from, the antenna systemsI and 8 by device 28. Also,

a slight increase in the higher order minor lobes T5 88 but, because ofthe intensity increase in the major lobe 88, that is, becauseof thelarge am plitude along axis 8 of the principal lobe I8 I, these higherorderminor lobes 88 are in a sense restored to normal.

Considering in detail the E-plane resultant patterns 8| and 82, Figs. 8and 7, note that the pattern 8!, Fig. 8, includes a pair of deep nullsI82 at the angular directions corresponding to'the first minor lobes 81which, in the main antenna pattern 88, have amplitudes of 28.7 per cent.Hence, by reason of the action of the auxiliary antenna, the first minorlobes 81 are obliterated. The subsidiary lobes I88 and I84, Fig. 6; ofthe resultant pattern 8! are slightly greater than the higher orderminor lobes 88 of the main antenna pattern 88, because of the blockingeffect of the auxiliary reflector I8 and because of the fact that in theparticular embodiment tested the auxiliary pattern 88 oyerlaps-to someextent the higher order mlnor-lobes 88. The subsidiary lobes I88 and I84are about 10 per cent of the single trip or one-way resultant principallobe II" and about 1 per cent of the calculated round-trip or two-wayprincipal lobe which is illustrated in Fig. 12. In Fig. 7, the leftfirst minor lobe 81, which increased with beam shift, is in effectdecreased from 48.5 per cent to 13.0 per cent in the resultant pattern,corresponding'to the value of the left first subsidiary lobe I88, Fig.7. The right first minor lobe 81 of 9 per cent is decreased almost tozero as shown by the value of the right first null I82 of pattern 82,Fig. '7. The right; higher order minor lobe 88, Fig. '1, of 19.5 perdent is in effect reduced to 15.2 per cent which corresponds to thevalue of the right first subsidiary lobe I88, while the left higherorder minor lobes 88 are increased somewhat, but confined to a maximumamplitude of per cent.

Referring to the H-plane resultant patterns 88 and 84, Figs. 8 and 9,the left and right first minor lobes 81 of pattern 81, Fig. 8, whichhaveamplitudes of 28.5 per cent, are in effect transformed into firstsubsidiary lobe's I88 having amplitudes of about 12.8 per cent. In Fig.8the left first minor lobe 81,'which increased to 45.8 per cent inamplitude with the lobing', is converted 'to the left first subsidiarylobe I88, the maximum amplitude of which is about 14.5 per cent; andtheright first minor lobe 81, which decreased to 23.8 per right firstsubsidiary lobe I88 having a 18.3 per cent amplitude.

Actually, the first minor lobes 81 in the H-plane patterns, Figs. 8 and9, are each a combination of the first and second minor lobes. E-planethe first and second minor lobes have opposite phases, it has beemfoundin testing one embodiment that in the H-plane the first and second'minor lobes have quadrature phases and therefore merge to form the largesecondary lobes 81 which are shown in Figs. 8 and 9, and have beendesignated as first" minor lobes. Note that in Fig. 8 the secondarylobes 81 are, at the 70 :18 degree peak amplitude, reduced to zero ornulls I 82in the resultant pattern, but that fairly prominent firstsubsidiary lobes I88 are aligned with certain off-axis or off-peakdirections included in the secondary lobes 81 and having minor amplitudevalues. The presence of the relatively the blocking action of theauxiliary antenna system 8 causes.

cent in amplitude, is in effect changed to-the* While in theprominentfirst subsidiary lobes I08, in each of Figs. 8 and 9, indicates that themaximum lobe 89 of the auxiliary antenna is merging with the secondminor lobe 98 (not shown) which is in phase quadrature with the maximumlobe. As a result, while in the E-plane patterns, Figs. 6 and 7,substantially complete elimination of the first minor lobes 91 isefiected, in the H-plane, the reduction is not entirely complete. Ifonly the directive operation in the H-plane is of interest, a compromisephase adjustment of the auxiliary antenna system may be made for thepurpose of further decreasing the H-plane secondary lobes 91.

It should be pointed out that, in accordance with the invention, theminor lobe reduction is obtained with only a small increase in the mainbeam width. As shown in Figs. 6 and 7, in the.

E-plane, at the half power or 50 per cent point of the principal andmajor lobes, the increase is from 12 to 13.5-degrees or about 12.5 percent. In the H-plane, Figs. 8 and 9, the increase in main beam width atthe half power point is from 13.9 to 15.6 degrees or 12.5 per cent. Ineach plane, this increase in width is relatively small as compared tothe to per cent increase in main beam width produced by the prior artmethod of minor lobe reduction which involves tapering the illuminationof a reflector. Such an increase in the beam width is not desired,particularly because the gain of the antenna, for a given aperture, isreduced.

In addition, it should be noted that by reducing the first minor lobes,in accordance with the invention, the region close to the main beam isalmost free of radiation. Hence, when the main beam is switched, falsecrossovers" cannot occur between'the main beam and the first minorlobes; and, as is desired, the only crossover is on axis 6 and betweenthe two main beam positions. The true or desired crossover is the pointon axis 8 at which the resultant lobe, in its up position, intersectsthe resultant lobe, in its down position. To illustrate, when the priorart pattern 88, Fig. 8, is reversed, the true crossover occurs on axis6. In addition a false crossover occurs only 11 degrees from and on eachside of axis 8. The false crossover is between the major lobe and thefirst minor lobe and its amplitude is about 38.5 per cent one way.Another false crossover occurs at i 26 degrees with an amplitude of 23per cent one way. The false crossovers may produce, of course, false orambiguous indications'on the train (rightleft) indicator or theelevation (up-down) indicator in the radar transceiving device 28. Inthe system of the invention, which has the resultant pattern 96, Fig. 9,there are no crossovers in the i 21 degree region, and, outside oi thisregion, the maximum false crossover amplitude is relatively low, namely,8.2 per cent one way.

It may also be stated that the band width characteristic of the systemof Figs. 1, 2 and 3 is highly satisfactory. A frequency test of theembodiment of Figs. 1, 2 and 3 mentioned above showed that, over the920-970 megacycle band, the angular sensitivity of the system is, as isdesired, substantially constant over the above band or range, and thepatterns are also almost constant.

Calculated two-way patterns The two-way patterns of Figs. 10, 11 and 12were obtained by calculating the echo amplitude received afterreflection by a distant target. Figs. 10 and 11 illustrate the E-planeand H- plane resultant patterns, respectively, when the beam is lobed tothe right position: and Figs. 12 and 13 illustrate the E-planeandH-plane patterns. respectively, when the beam or resultant lobe isswitched to the up position. When the beam is lobed to the leftposition, the E-plane and H-plane patterns of Figs. 10 and 11 areeachreversed: and when the beam is lobed to the down position, theE-plane and H-lplane patterns of Figs. 12 and 13 are each reversed. Inthese four figures the reference numeral I05 denotes the resultantpattern for the system'oi' the invention comprising a main antennasystem and an auxiliary antenna system 9 and numeral I66 denotes thepatterns for the main antenna system I taken alone. Numerals I01 denotethe principal lobe, numerals I08 t e first nulls and numerals I09 thesubsidiary lobes of the resultant patterns I06. Numerals IIO denote themajor lobes and numerals II I the first minor lobes of the main antennapatterns I06.

, Considering the two ill-plane patterns I06, Figs. 10 and 12, themaximum amplitude of the first minor lobes III for these two pattern-sis 19.2 per S0 tude from about 84-, to V42 of the maximum inmumintensity of the first minor lobes III is about 20.8 per cent and theauxiliary antenna reduces this intensity to 2.1 per cent, that is, fromabout V5 to about ,3 of the maximum intensity of the principal lobeIII'I. In general, in Figs. 10, y

11, 12 and 13, the first minor lobes III are completely eliminated orsubstantially reduced.

It has thus been shown that in accordance with the invention, asatisfactory directive characteristic is secured which is of highutility, not only in the radar art but also in the radio, telephoneand'telegraph arts. If desired, in radar operation, the main antenna maybe disconnected from de vice 28 by suitable switching and the auxiliaryantenna may be utilized as a "search" antenna for roughly locating thetarget direction. After the search operation is completed. the twosystems may then be utilized for-accurate dual plane lobe switching.

Although the invention has been described in connection with aparticular embodiment, it is not to be limited to this embodimentinasmuch as other apparatus may be successfully employed in practicingthe invention.

What is claimed is:

1. A method of reducing or obliteratin at least one minor lobe in anantenna direc ive characteristic, which comprises aligning a directionof action of a lobe of another directive character-let's with thedirection of, maximum action or axis of said minor lobe, substantiallyequal zing the two lobe intensities. and rendering said lobesantiphasal.

2. A method of materially reducing at least one minor lobe in thedirective pattern of a main antenna system which comprises align ng adirection of action in the maximum lobe of. an auxiliary antenna-withthe direction of maximum action of said minor lobe, substantiallyequalizing the intensities of said lobes in-the aligned directions, andrendering said lobes antiphasal.

3. A method of reducing the two cophasal first minor lobes flanking themajor lobe in the directive characteristic of a main antenna system.

utilizing an auxiliary antenna having a maximum lobe the angular widthof which is at least as great as the combined angular width of the threeflrstmentioned lobes, which comprises aligning the direction of greatestaction oi said maximum lobe with a direction included in said majorlobe. substantially equalizing the intensities of said maximum lobe andsaid minor lobes, and rendering .said maximum lobe'and said minor lobesantiphasal.

4. A method of substantially reducing at least one of the first minorlobes adjoining the major lobe -in the directive pattern of aunidirective main antenna system connected to a translation device,utilizing a unidirective auxiliary antenna system having a maximum lobethe angular width of which is as great as the angular portion of thepattern including said first-mentioned lobes and the null positionedtherebetween, said auxiliary antenna being connected to said devicethrough an adjustable attenuator for regulating the intensity of saidmaximum lobe and through an adjustable phase shifter forcontrolling thephase of said maximum lobe, which comprises aligning the axis of saidmaximum lobe with a direction of action included in said major lobe,adjustingsaid attenuator so as to equalize the intensities of saidmaximum lobe and said minor lobe, and adjusting said phase shifter so asto secure a maximum lobe having a phase opposite to that of said minorlobe.

5. In combination, a pair of antenna systems connected through separate,lines to the same translation device, one of said antenna systems vhaving a minor directive lobe and the other antenna system having amaximum directive lobe. a direction of action in said maximum lobe beingaligned with the axis or direction of greatest action in said minorlobe, a phase shifter included 6. In combination, a pair of antennasystems,

connected through separate lines to the same translation device, one ofsaid antenna systems having a major directive lobe interposed between apair of cophasal directive minor lobes and having a phase opposite thatof said minor lobes, the other antenna system having a maximum directivelobe aligned with said major lobe, the width of said maximum lobe beingsubstantially equal to the combined widths of said major lobe and-saidminor lobes, and means comprising a phase shifter and an attentuatorincluded in one of said lines (or rendering said maximum lobe andsaidminor lobes antiphasal and for equalizing substantially said maximumlobe and said minor lobes.

7. In combination, a translation device, a main antenna systemcomprising a pair of parabolic reflectors, separate primary antennas atthe fool of said reflectors, a flrst line connecting said primaryantennas to said device, an auxiliary antenna system comprising aparabolic reflector, a separate primary antennaat its focus, a secondline connecting said last-mentioned primary antenna to said device, saidthree reflectors facing the, same direction and having parallel axesincluded in the same plane. the aperture dimension in said plane oi eachof the main antenna reflectors being greater than the aperture dimansionin said plane oi. the auxiliary antenna reflectors, the directivepattern of the'main antenna in a plane of radio action perpendicular tothe first-mentioned plane including a narrow 'major lobe interposedbetween a pair of cophasal minor lobes having a phase opposite to thatof the major lobe, and the directive pattern of the auxiliary antenna insaid plane of action being the two minor lobes substantially equal tothe intensities of said minor lobes. 9. A combination in accordance withclaim 7, an adjustable phase'control means inserted in one of said linesfor rendering the phase of the maximum lobe equal to that or the majorlobe and diilerent from that or the cophasal minor lobes. i

10. A combination in accordance with claim 7,

an adjustable amplitude controlmeans inserted in one of said lines andan adjustable phase control means inserted in one oi! said lines,whereby said minor lobes may be greatly reduced and, the minor lobes ofthe combined directive pattern of the two antenna systems may berendered negligible.

11. In combination, a translation device, a-

main antenna system comprising a pair of parallel linear arrays eachcomprising a plurality of spaced antenna elements, a first lineconnecting all 01' said elements to said device, an auxiliary antennasystem comprising a linear array of elements, a-second line connectingthe last-mentioned elements to said device, the plurality of elements ineach of the two first-mentioned arrays being greater than the pluralityof elements inthe last-mentioned array, said main antenna having in oneplane of radio action a directive pattern including a narrow major lobeinterposed between two cophasal minor lobes, the phase of the minorlobes being different from that of the major lobes, and the directivepattern of said auxiliary antenna in said plane or action being alignedsubstantially with the first-mentioned directive pattern and including amaximum lobe having a width substantially equal to the combined widthsof said major lobe and said minor lobes.

12. A combination in accordance with claim 11, an adjustable amplitudemeans inserted in one of said lines.

13. A combination in accordance with claim 11, an adjustable phasecontrol meansvinsertedin one of said lines.

14. A combination in accordance with claim 11, an adjustable amplitudecontrol means inserted in one of said lines and an adjustable phasecontrol means inserted in one of said lines.

15. In combination, a main antenna system and an auxiliary antenna eachcomprising a cylindrical parabolic reflector, said reflectors iacing inthe same direction and having parallel axes, the width and lengthdimensions of the main reflector being greater than the correspondingdimensions of the auxiliary reflector, separate primary antennas forsaid reflectors each comprising a linear array of antenna elementsaligned with the reflector focal line, the plurality of elements in theprimary antenna of the main system being greater than the plurality ofelements in the primary antenna of the auxiliary system, and means-forsimultaneously connecting all of said elements to a translation device.16. In a dual plane lobe switching system. a

' main directive antenna system comprising a large upper cylindricalparabolic reflector and a large lower cylindrical parabolic reflector, apair of linear subarrays aligned with the focal line of each reflectorand each comprising a plurality of dipoles, a translation device,separate lines connecting the four subarrays to said device, meansconnected to said lines for shifting the phase of the currents in two ofsaid lines simultaneously and in all of said lines successively, anauxiliary directive antenna system positioned adjacent to said mainsystem and comprising a small cylinattenuator, an, adjustable phasechanger, said changer.

CLIFFORD A. WARREN.

REFERENGES CKTED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,821,386 Lindenblad Sept. 1,1931 2,095,083 Renatus Oct. 5, 1937 2,342,721 Boerner Feb. 29, 1944FOREIGN PATENTS Number Country Date 706,661 Germany Jan. 17, 1936

